New TRPC6 gain-of-function mutation in a non-consanguineous Dutch family with late-onset focal segmental glomerulosclerosis
until further notice
SourceNephrology, Dialysis, Transplantation, 28, 7, (2013), pp. 1830-1838
Article / Letter to editor
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Nephrology, Dialysis, Transplantation
SubjectIGMD 3: Genomic disorders and inherited multi-system disorders; NCMLS 1: Infection and autoimmunity N4i 4: Auto-immunity, transplantation and immunotherapy; NCMLS 3: Tissue engineering and pathology IGMD 9: Renal disorder; NCMLS 3: Tissue engineering and pathology N4i 4: Auto-immunity, transplantation and immunotherapy; NCMLS 5: Membrane transport and intracellular motility IGMD 9: Renal disorder
BackgroundFocal segmental glomerulosclerosis (FSGS) is a leading cause of steroid-resistant nephrotic syndrome. Hereditary FSGS is frequently caused by mutations in important structural podocyte proteins, including the slit diaphragm-associated transient receptor potential channel C6 (TRPC6).MethodsIn five patients with biopsy-proven autosomal-dominant FSGS from five different Dutch families, all 13 exons of TRPC6 were sequenced. Upon identification of a novel TRPC6 sequence variant, the resultant amino acid change was introduced in the wild-type TRPC6 protein and functionally tested using patch-clamp analyses and cell-surface biotinylation experiments.ResultsNone of the previously described TRPC6 mutations were found in our cohort. In one family, we identified a novel c.524G>A sequence variant resulting in a p.Arg175Gln (R175Q) substitution in the TRPC6 protein. This sequence variant was absent in 449 control subjects and from public SNP databases. The mutation was located in the third ankyrin repeat domain (ANK3) in the cytoplasmic N-tail of TRPC6, important for protein-protein interaction and regulation of ion channel activity. Patch-clamp analyses of the mutant channel indeed showed an increased TRPC6 channel-mediated current. However, cell-surface expression of the mutant channel was not increased.ConclusionsWe identified a novel TRPC6 p.Arg175Gln gain-of-function mutation that shows increased TRPC6-mediated current, which is not due to altered cell-surface expression. This is the first mutation identified in ANK3 of the TRPC6 N-tail and is most likely responsible for the late-onset autosomal dominant FSGS in this family.
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